Although InP and GaAs based HBT Integrated Circuit (IC) technologies have demonstrated great potential in high-speed digital and mixed-signal applications because of superior speed and bandwidth properties over the SiGe based HBT technology, up to now InP and GaAs based HBTs with high Ft and with high BVceo could not be built on a common wafer because they require different collector profiles. HBT layer structures with various collector profiles are not available on the same substrate.
SiGe based HBT technology of various collector concentrations available on same chip has been described in the prior art. See for example G. Freeman et al, “Device scaling and application trends for over 200 GHz SiGe HBTs”, 2003 Topical Meetings on Silicon Monolithic Integrated Circuits in RF Systems, pp. 6-9, Digest of papers. The SiGe based HBT technology enables high Ft to be traded for high BVceo on the same chip. However, IC designers up to now could not trade high Ft for high BVceo or vise versa on same InP or GaAs wafer.
Ability to provide high Ft HBTs and high BVceo HBTs on the same chip is particularly useful in smart Power Amplifiers (PAs) in millimeter wave image radar. Increased power provides longer distance of operation. Smart PAs with digital electronics to control the PAs can be realized by high speed signal processes for regular logic and high BVceo (breakdown voltage) for large swing at the output stage. However, presently, when high BVceo HBTs are used in logic circuits lower speed may occur as compensation due to inability to serve as high Ft HBTs in logic circuits on the same chip.
Ability to provide high Ft HBTs and high BVceo HBTs on a common chip substrate is also useful in the front-end stage of an analog to digital (A/D) converter. Having high Ft HBTs and high BVceo HBTs on common chip substrate provides increased dynamic range and larger input to analog converter which is advantageous for higher signal/noise (S/N) ratio and resolution. However, A/D technologies of today cannot provide significantly higher peak-to-peak input signal than 1V with good linearity. Better dynamic range will certainly improve this technology.
Accordingly there is a need of fabricating and integrating high Ft HBTs and high BVceo HBTs on the common non-silicon based wafer and chip.